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Response to Barraclough et al. on ‘Degree‐of‐spread artefact in the NSW Central Cancer Registry’

Response to Barraclough et al. on ‘Degree‐of‐spread artefact in the NSW Central Cancer Registry’ We note the important paper by Barraclough et al. describing an artefactual increase in cancer cases recorded with unknown degree‐of‐spread (stage) in the NSW Central Cancer Registry for the period 1993 to 1998 and its potential impact on analyses that require stage adjustment. We would like to provide some additional information on the accuracy of the Cancer Registry's stage information and its potential impact on stage adjustment. In a study comparing colorectal cancer stage recorded in the NSW Central Cancer Registry, with that from a survey of treating surgeons, we found that the overall agreement between the registry stage and survey stage was 69.5%. The registry stage appeared biased towards over‐reporting of localised disease and spread to regional lymph nodes and under‐reporting of spread to adjacent tissues and distant metastases. As the patients included in the comparison were diagnosed between 1 February 2000 and 31 December 2000, the result does not relate to the artefact period but indicates important, possibly ongoing, stage misclassification. This had an important impact on estimates of spatial variation in stage‐specific colorectal cancer survival. The probable stage misclassification that we have described and the staging artefact that Barraclough et al. have described could have had an impact on our examination of trends in stage adjusted survival from cancer in NSW. We acknowledged this at the time: “These considerations notwithstanding, there remains justifiable concern about the impact of the increase in the proportion of unknown stage cancers on our adjustment for stage of cancer and especially the possibility that the distribution of stages within this unknown stage group may also have changed with time, a possibility we cannot rule out.” This acknowledgement notwithstanding, we now consider it unlikely that the staging artefact had an important effect on the trends in survival we reported. An examination of our data for evidence of stage migration (a well‐recognised artefact in trends in cancer stage) showed that most of the observed increases in survival were present in all stage categories and that for most cancers overall survival, when unadjusted for spread of cancer, generally fell in parallel with that in the specific stage categories. In addition to ruling out important stage migration, this pattern also excludes an important effect of the reported staging artefact. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Australian and New Zealand Journal of Public Health Wiley

Response to Barraclough et al. on ‘Degree‐of‐spread artefact in the NSW Central Cancer Registry’

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References (9)

Publisher
Wiley
Copyright
© 2009 The Authors. Journal Compilation © 2009 Public Health Association of Australia
ISSN
1326-0200
eISSN
1753-6405
DOI
10.1111/j.1753-6405.2009.00348.x
pmid
19236369
Publisher site
See Article on Publisher Site

Abstract

We note the important paper by Barraclough et al. describing an artefactual increase in cancer cases recorded with unknown degree‐of‐spread (stage) in the NSW Central Cancer Registry for the period 1993 to 1998 and its potential impact on analyses that require stage adjustment. We would like to provide some additional information on the accuracy of the Cancer Registry's stage information and its potential impact on stage adjustment. In a study comparing colorectal cancer stage recorded in the NSW Central Cancer Registry, with that from a survey of treating surgeons, we found that the overall agreement between the registry stage and survey stage was 69.5%. The registry stage appeared biased towards over‐reporting of localised disease and spread to regional lymph nodes and under‐reporting of spread to adjacent tissues and distant metastases. As the patients included in the comparison were diagnosed between 1 February 2000 and 31 December 2000, the result does not relate to the artefact period but indicates important, possibly ongoing, stage misclassification. This had an important impact on estimates of spatial variation in stage‐specific colorectal cancer survival. The probable stage misclassification that we have described and the staging artefact that Barraclough et al. have described could have had an impact on our examination of trends in stage adjusted survival from cancer in NSW. We acknowledged this at the time: “These considerations notwithstanding, there remains justifiable concern about the impact of the increase in the proportion of unknown stage cancers on our adjustment for stage of cancer and especially the possibility that the distribution of stages within this unknown stage group may also have changed with time, a possibility we cannot rule out.” This acknowledgement notwithstanding, we now consider it unlikely that the staging artefact had an important effect on the trends in survival we reported. An examination of our data for evidence of stage migration (a well‐recognised artefact in trends in cancer stage) showed that most of the observed increases in survival were present in all stage categories and that for most cancers overall survival, when unadjusted for spread of cancer, generally fell in parallel with that in the specific stage categories. In addition to ruling out important stage migration, this pattern also excludes an important effect of the reported staging artefact.

Journal

Australian and New Zealand Journal of Public HealthWiley

Published: Feb 1, 2009

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